The present invention relates to a front wheel suspension for a vehicle having only one front wheel, by which is primarily meant a motor cycle. In the front wheel suspension, the wheel is mounted in at least one preferably rearward-sloping supporting member which, with the aid of or via bearing units comprising link elements and possibly a springing function, is/are in turn mounted on the chassis of the vehicle. The bearing units allow springing motions in a springing direction for the supporting member, produced by means of connection to a shock absorber or spring function. The bearing units also effect torsional rigidity against the cross-directional action of the supporting member relative to the chassis, viewed in the longitudinal section of the vehicle. Moreover, the bearing units forcibly steer the supporting member in its motions in the said longitudinal section during the said springing motions.
A resilient front wheel suspension on, for example, motor cycles is currently realized principally as a telescopic springing or telescopic fork in which inner tubes and outer tubes are mutually longitudinally displaceable and supported one upon the other by means of bushes. The wheel is in this case mounted in the one tube or tubes, whilst the other tube or tubes is/are secured in the chassis. The securement in the chassis is usually realized in connection with a so-called fork crown (triple clamp) to which also the handlebar of the motor cycle is secured. The known arrangement operates with a steering joint and a sliding joint. The telescopic arrangement is rearward-sloping and a steering line for the motor cycle is likewise sloping (essentially parallel with the sloping of the telescopic arrangement) and extends down through the centre of turn of the handlebar, somewhat to the side of the centre of turn of the wheel and further down to a position on the ground plane or the support surface somewhat in front of the point of contact of the wheel with the ground plane or support surface (compare the concept xe2x80x9ctrailxe2x80x9d). The term xe2x80x9csteering linexe2x80x9d constitutes a recognized concept and purely general reference is made to this. The bearing of the telescopic arrangement is realized at a relatively high level above the ground plane. Upon braking of the wheel, the securement is acted upon by torque. Moreover, the braking gives rise to a weight displacement force which endeavours to compress or boost the compression of the telescopic arrangement in a dive motion. Additional forces generated in the braking of the motor cycle can hereupon produce up to double jounce motions. The telescopic arrangement can be realized with different or desired springing or motion geometries. This term too is a recognized concept, to which purely general reference is made. Thus, for example, the motor cycle/telescopic arrangement can be provided with special so-called xe2x80x9canti-divexe2x80x9d arrangements, which oppose or produce desirably low dive effects in the event of braking actions with or on the front wheel. The telescopic arrangement has a relatively low rigidity and can be subjected to torsional oscillations of a self-oscillation nature (wobbling), which have to be compensated with component(s) in one way or another. High clamping loads can arise in the said fork crowns (upper and lower fork crowns). The inner and outer tubes in the telescopic arrangement are often long and the lateral forces upon the tubes mean that these can be locked to one another in certain travel situations in which the locking can occur by way of the bushes.
With a view to overcoming the weaknesses of the telescopic arrangement, in vehicles/motor cycles of this kind, attempts have been made to replace the telescopic fork with various types of link systems. Reference is made, inter alia, to the magazine xe2x80x9cMotorcyclist/January 1987xe2x80x9d, pages 47-53, which shows a variety of resilient front wheel suspensions with link systems which are intended to replace the springing function produced with the telescopic fork, which link systems are disposed between wheel supporting member(s) and the chassis. Reference is also made to the so-called xe2x80x9cWebbxe2x80x9d fork, which was used on motor cycles during the period 1920-1940.
It is also conceivable to try to transfer wheel suspension principles from four-wheeled vehicles (cars) to the present context. There are however no acceptable working proposals in existence for such transfers.
There is a general need to be able to eliminate all the drawbacks attached to the use of various telescopic fork constructions. Thus, for example, a greater freedom of choice is sought with regard to the procurement of a desired spring geometry, which will be able to be realized, moreover, without the use of complex and expensive additional components. The risk of self-oscillations (wobbling) at certain vehicle speeds has to be able to be effectively eliminated by simple means. There is also a need to be able to reduce the clamping forces in the securements of the wheel-supporting member in the chassis, inter alia by means of the facility to arrange separate securement functions at a relatively low height above the ground surface and thereby avoid tightly spaced bearing points high up in connection with the handlebar. There is also a requirement to be able to eliminate the need to mutually separate springing elements and steering linkage, in which the steering linkage hitherto often had to be relatively weakly dimensioned on structural engineering grounds, inter alia with a risk of the said self-oscillation tendencies within certain of the speed ranges of the vehicle. The invention sets out to solve these problems, inter alia, by proposing bearing or link units which produce distinct positions and motion diagrams for the supporting member by exhibiting high rigidity in certain directions and by exhibiting compliance for torsion or twisting motions which arise in the bearing unit arrangement in the event of torsional steering motions of the supporting member.
In connection with the introduction of the said link unit functions, it is important to overcome the deficiencies which hitherto attach to known link unit arrangements. A major drawback with these is a substantially reduced contact sensation for the driver between the handlebar and the ground surface or roadway. The invention sets out to solve this problem also and proposes a front wheel suspension offering contact sensation characteristics between the handlebar and the roadway equivalent to those which obtain with telescopic arrangements.
The known link unit systems additionally have relatively complex structures for the springing and steering functions per se and/or for components proposed to form part of these functions. The invention sets out to solve this problem also.
In certain types of motor cycles, for example special-purpose motor cycles, cross-country motor cycles, etc., it is important to be able to propose symmetrical wheel suspensions which can allow large wheel deflections or wheel turns. The use of swivelled-out links which extend by the side of the wheel is therefore inadmissible, but rather the link arrangement must be able to be applied above the front wheel so that it is as low as possible above the ground plane. The invention solves this problem also.
According to the present invention, the spring geometry (or the motion geometry) shall be adjustable by the choice of lengths of the bearing units and/or of the link elements and/or of their reciprocal angles and/or angles in relation to a horizontal line, everything viewed in the longitudinal section of the motor cycle (or vehicle) in question in, for example, upright or standing position. The invention solves this problem also.
According to the present invention, bearing unit(s) forming part of the subject of the invention shall be able to be arranged with certain compliance for certain torsion or twisting motions. The invention solves this problem also and proposes measures for the structure and choice of material in the unit(s) concerned, which measures produce an expedient compliance function.
According to the invention, two link units shall be able to be used in a mutual functional interplay, when the supporting member (the wheel) is steered up in spatial terms, and shall hence clear the way for an improved and expedient steering of the motor cycle in co-existence with an expedient springing function. The invention solves this problem also.
According to the invention, the chassis shall be able to bear and steer the supporting member with mounted front wheel without giving rise to risks that the supporting member will oscillates or move around its securements in the chassis, everything viewed in a horizontal section through the motor cycle, the link units and the supporting member. The invention solves this problem also.
In one embodiment of the invention, in a lower link unit a ball joint bearing is used in the securement of the link unit in a wheel-supporting member. Standard ball joints are already produced for this purpose, which can therefore be used in the present invention.
A front wheel suspension according to the invention can principally be deemed to be characterized in that the bearing units mentioned in the introduction consist of mutually separate upper and lower bearing units, which are provided with bearing members in or about which the said supporting member(s) and hence the wheel are turnable. The first of (or one of) the said upper and lower bearing units acts as a combined bearing and steering link member for the said wheel supporting member(s) and the wheel. The said first bearing unit is further arranged compliantly for torsion or turning motion which arises in the first bearing unit when the said supporting member(s) and the wheel are allotted steering or turning motion or assume a steering or turning position which differs from the longitudinal axis of the vehicle (i.e. where the steering deflection=0).
The upper bearing or link unit can in its horizontal view be configured as a tetragon (square, rectangle, trapezium, etc.), the securement points of the link unit in the supporting member(s) being situated at the two front corners and the securement points of the link unit in the chassis being situated at the rear corners.
In a preferred embodiment, the bearing member of the first or the upper bearing or link unit is secured to the rear parts of the link unit by or by means of a first bearing which extends in the longitudinal direction of the link unit and which can here comprise a transverse first bearing axle. The said supporting member(s) can be mounted on the upper link unit on the front parts thereof by or by means of a second bearing, for example a second bearing axle, which likewise extends in the transverse direction of the upper link unit. The said torsion or turning motion in the said plane through the upper link unit induces opposite turning or actuation motions on the first and second bearings or the bearing axles about an imaginary longitudinal axis through the plane (which longitudinal axis coincides with the longitudinal axis of the vehicle). Also included in the said preferred embodiment is that the bearing member of the upper link unit has a first part (bearing part) which coincides with the steering line, mentioned in the introduction, in the said initial position for the springing function and which can be mounted in a bearing housing secured to the chassis. The bearing member of the upper link unit can also comprise a pivoted second part, viewed in the longitudinal section of the vehicle, which at the back (i.e. in the direction of the rear parts of the vehicle) passes into interaction with the said first bearing or bearing axle. The pivoted second part can widen rearwards in its latitudinal direction so as to acquire a width at the back which essentially corresponds to the rear width of the upper link unit. The springing function of the upper link unit can thus be able to be effected by means of link elements extending in the forward direction of the link unit. With the securing function(s) of the link elements in the said first and/or second bearing(s) or bearing axle(s), rotatable bearing functions are created. The first part of the bearing member can be mounted in a bearing housing containing one or more ball bearings and the longitudinal axis of the first part coincide with the said steering line in an initial position for the springing function.
In one embodiment, the bearing member of the lower link unit is configured such that it consists of or comprises a ball joint. The lower link unit can further have an essentially triangular horizontal view in which the bearing member/ball joint of the lower link unit is situated at the apex of the triangle and the securement point(s) to the chassis is/are situated at the corners on the base of the triangle. The rear bearing of the link unit, which, for example, can be constituted by one or more bearing axles, extends in the transverse direction of the vehicle, for example along the whole or parts of the base of the said triangle. A springing-effecting function can herein be arranged on or in the bearing members and/or securements of the lower link unit in the said wheel-supporting member or chassis. In addition, sought-after spring geometry (or motion geometry) for the supporting member can be able to be chosen by means of longitudinal extent(s) on the link elements of the link units in the principal longitudinal sections of the link units or vehicle. The spring geometry pursued by means of the link units can also, by way of supplement or alternative, be choosable by means of mutual angular adjustment(s) relative to a horizontal line through the longitudinal section of the vehicle between or for the link elements extending in the longitudinal direction of the vehicle. The steering-up function can further be able to be chosen by means of sizing of the dimensions of the first and/or second bearing parts and/or by means of choice of material. The said dimensions can herein relate to diameter or diameters, width and/or thickness and the said choice of material can relate to metal, composite, alloy, etc.
In a preferred embodiment, the rigidity of the bearing or link units in their respective horizontal planes is chosen by means of the link elements of the link units, which link elements extend in the transverse direction, and/or the constitution or thicknesses of the link elements and/or choice of material. In a preferred embodiment, the upper link unit consists of or comprises a U-beam shaped link element in, for example composite, alloy or metal material. The first and second bearings or bearing axles can here be arranged on the rear and front sides of the U-beam. The upper and lower link units can further be configured to prevent the occurrence of significant oscillation tendencies for the supporting member(s) in the horizontal plane of the link units in relation to the securement points or the respective bearing in or on the chassis. Alternatively, the first bearing unit can be constructed from individual link elements, for example two side link elements connected by means of a diagonal link element. The said spring geometry operates with springing motion for the wheel/supporting member(s), which is made up of a motional component coinciding with the rearward slope or the steering line and a motional component which has a part which is substantially vertical or which coincides in the vertical direction or longitudinal section of the vehicle. The wheel can be non-resiliently mounted in the said supporting member(s). The upper link unit can also be constructed to support the handlebar, steering wheel or equivalent of the vehicle. Both the link units are further preferably situated above the wheel and the lower link unit is situated directly above the wheel. The number of supporting members can be two and the wheel is mounted between the supporting members. The twisting or the torsion motion of or in at least the first link unit is related to allotted steering force, which can be progressively or linearly increasing in dependence upon the wheel turning position. The lower bearing element can be constituted by a leaf spring or wing damper arrangement which is secured to the supporting member by a ball joint and articulated, or be secured by a torsion or wing damper function to or with a bearing belonging to the chassis. The wheel suspension members are elongated and can in one embodiment be configured so as to imitate the forks in a conventional telescopic fork structure.
As a result of that which has been proposed above, new paths are opened up for being able to achieve resilient and well-defined suspension systems for front wheels, for example on motor cycles, which suspension systems are technically sound and are developed from economically beneficial components. Reliable link elements units comprising link elements can be used and the number of components in the link units can be constituted by just a small number of components. Composite, metal and/or alloy material can be used in an noncritical manner. The appearance of the telescopic function or telescopic fork can easily be imitated. Similarly, the advantages of the telescopic function (such as the sensitivity with the ground surface) can be utilized, whilst at the same time all its disadvantages are eliminated. Similarly, the advantages of the known link unit systems can be utilized, whilst at the same time all its disadvantages of complexity, expensive components, link element tractions which impede wheel manoeuvring and, in the course of driving, of relatively large wheel turning steer-outs according to the above, are eliminated. Large parts of the new link system arrangement can be constituted by standard elements and tried and tested material.
As a result of the invention, the bearing function of the upper link unit for the wheel supporting member(s) is put together with previously used separate linkage, which clears the way for a technically simple and economical solution. Weight displacement due to braking can effectively be prevented from having a prominent effect upon the springing function, for better driving safety. The link element structure proposed in one embodiment is extremely advantageous and offers a host of structural engineering advantages with exceedingly good springing and steering characteristics for the motor cycle. The wheel suspension system can be used on all types of motor cycles, including motor cycles for road usage. A torsionally rigid and simple wheel supporting member suspension is therefore present in the chassis, combined with good springing functions for the member(s) and the front wheel.